1. Field of the Invention
The present invention relates to a floppy disc drive (FDD) chucking device which uses a reliable and low-cost means for centering a floppy disc for rotation when loading the floppy disc into the floppy disc drive.
2. Description of the Related Art
Record media (typified by floppy disks), that is, disc cartridges, are loaded into a floppy disc drive. A disc cartridge is a case containing a thin record disc. In a floppy disc drive, the record disc is rotated, and input operations of record data and output operations of recorded data are carried out through a write/read window (which opens to the case) provided with a shutter. A floppy disc drive must be capable of allowing easy removal of the record disc contained in the case from the floppy disc drive, precisely aligning the record disc with the axis of rotation of the floppy disc drive during write/read operations, and precisely controlling the rotational speed of the record disc. To achieve these, a chucking device, such as that shown in FIGS. 5 and 6, has been conventionally used in floppy disc drives.
A record disc, or a floppy disc, has a center hub at the center portion thereof. In FIGS. 5 and 6, the center hub 2 has a substantially square center hole 3 formed in the center portion thereof, and a substantially rectangular hole 4 formed in a peripheral edge portion thereof. The hole 4 is defined by a front edge 4a (being formed in correspondence with the front portion of a rotor yoke in the direction of rotation thereof) and an outer edge 4b (formed away from the center of rotation of the rotor yoke). In the specification, the direction away from the center of rotation of the rotor yoke is referred to as the outward direction.
A floppy disc drive includes a rotor yoke 101, which is a ferromagnetic metallic disc rotationally driven by a motor (not shown) in a certain direction (in the direction of arrow D in FIGS. 5 and 6). A magnetic disc (or a chucking magnet) 102 is affixed to the top portion of the rotor yoke 101.
A center shaft 103 is provided in a standing manner at the rotational center 0 of the rotor yoke 101. It passes through a hole 102a formed in the center portion of the magnetic disc 102. It is provided so as to be loosely inserted into the center hole 3 formed in the center hub 2.
In the specification, the term "loosely" will be used to describe a state in which the center shaft 103 can move freely horizontally and vertically within a predetermined range.
An arc-shaped drive pin through hole 104 is formed in a peripheral edge portion of the rotor yoke 101, along a circumference of the rotor yoke 101. An arc-shaped chucking arm 105 is loosely provided in the drive pin through hole 104. It is formed by molding, along a circumference of the through hole 104. An upwardly extending drive pin 106 is formed on an end portion (hereunder referred to as the "front portion") 105a of the chucking arm 105 oriented in the rotational direction D of the rotor yoke 101. The drive pin 106 loosely passes through a front portion opening 102b formed in the magnetic disc 102. It is provided so as to be loosely inserted into the hole 4 formed in the center hub 2. On the front portion 105a are formed flanges 105c and 105c, which support the front portion of the chucking arm 105 so that the chucking arm 105 can move horizontally and vertically within a predetermined range. When the front portion of the chucking arm 105 is movably supported, the portion of the rotor yoke 101 located adjacent the front portion of the drive pin through hole 104 is loosely disposed between the flanges 105c and 105c.
From a back end of the drive pin through hole 104 formed in the rotor yoke 101, the other end portion (hereinafter referred to as the "back portion") 105b of the chucking arm 105 extends towards the back, along the top surface of the rotor yoke 101 so as to form an L shape. In a back portion opening 102c formed in the magnetic disc 102, a sliding shaft 108 which protrudes from the top surface of the rotor yoke 101 is received by a receiving hole 105d, thereby allowing the back portion of the chucking arm 105 to slide horizontally within a range corresponding to the width of the drive pin through hole 104, with the sliding shaft 108 as center.
A ferromagnetic plate 109 is mounted to the top portion of the body of the chucking arm 105, and functions to magnetically attract the entire chucking arm 105, so that the drive pin 106 is pushed upward at all times.
When a floppy disc is loaded into the floppy disc drive, a record disc is placed on top of the rotor yoke 101. The center hub 2 of the record disc is magnetically attracted to the magnetic disc 102, and the center hole 3 formed in the center hub 2 receives the center shaft 103 disposed at the rotor yoke side. Here, the drive pin 106 which protrudes above the magnetic disc 102 does not have to be inserted into the hole 4 formed in the center hub 2. When the drive pin 106 is not inserted in the hole 4, it is pushed by the center hub 2 to the level of the lower surface of the center hub 2, against the force of attraction of the ferromagnetic plate 109.
Here, within the time the rotor yoke 101 rotates not more than once in the direction of arrow D as a result of starting a motor (not shown), the top portion of the drive pin 106 slidably rotates at the lower surface of the center hub 3, and moves upward into the hole 4 by the force of attraction of the ferromagnetic plate 109. When the drive pin 106 has moved upward into the hole 4, further rotation of the rotor yoke 101 in the direction of arrow D causes the chucking arm 105 to slide in the same direction that the drive pin 106 moves when the drive pin 106 moves away from the rotational center 0, by the centrifugal force produced by the rotation of the rotor yoke 101. This causes the drive pin 106 to come into contact with the outer edge 4b defining the hole 4. In addition, it slidably moves forward in the hole 4 by the rotational force of the rotor yoke 101 so as to come into contact with the front edge 4a defining the hole 4. Accordingly, the drive pin 106 comes into contact with and is supported by the front edge 4a and the outer edge 4b defining the hole 4.
At this time, the center shaft 103 comes into contact with and is supported by two adjacent sides 3a and 3b defining the center hole 3 of the center hub 2. The adjacent sides 3a and 3b oppose the drive pin 106, with the rotational center O being located between the two sides 3a and 3b. When the center of the record disc and the rotational center O of the center yoke 101 coincide when the center shaft 103 is supported by the two sides 3a and 3b, the chucking operation is completed. When the two centers coincide, the record disc, or the floppy disc, is not decentered, so that it can rotate precisely in accordance with the controlled rotational speed of the rotor yoke 101.
However, the above-described floppy disc drive chucking device has the following problems. When the above-described chucking arm 105 is used, it is necessary to form a sliding shaft 108 on the rotor yoke 101. Here, it is difficult to form sliding shaft 108 precisely to a required height. In addition, in order to mount the chucking arm 105 loosely, it is necessary to form a large drive pin through hole 104. Here, the rotor yoke 101 flexes when drive pin through hole 104 is being formed, resulting in increased surface movement of rotor yoke 101.
The method of supporting the drive pin 106 by the front edge and the outer edge defining the hole 4 formed in the center hub 2 relies only upon the rotational moment of the chucking arm 105. Here, sliding friction produced between the chucking arm 105 and the rotor yoke and sliding friction produced between the magnetic head and media prevent the center shaft 103 from coming into contact with the two adjacent sides 3a and 3b defining the center hub center hole 3. The record disc may start to rotate continuously even though the center shaft 103 is not in contact with the two sides 3a and 3b. This means that the record disc is not centered when it rotates continuously, resulting in read/write operation errors.
In addition, it is troublesome to incorporate the chucking arm 105, resulting in increased manufacturing costs.